"It is not a question of syntactic cases, but of semantic actants. Every
verb has its own scheme."

I am not sure what you mean by a "semantic actant", I have made a brief
search of the internet, but cannot find anything where it talks about
only "four core arguments". It would be instructive if you could list say
about twelve verbs with their core arguments.

What about "part-exchange"

I part-exchanged my car.

Doesn't this imply everything that the word "sell" implies, and other

1. there is a seller, the one who sells.
2. there is a buyer, the one to whom sth is sold)
3. there is a "something" that is for sale
4. there is a price, expressed in some abstract unit.
5. the buyer possesses sth which has a lower value (in terms of the same
abstract unit mentioned in 4.)than the thing that is for sale.
6. A negociation is made between the buyer and seller to take the lower
valued item in partial payment.

I make that six core arguments.

Andrew Patterson.